Geology Highway Map Southern Ontario
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Commercial use includes commercial distribution of the Content, the reproduction of multiple copies of the Content for any purpose whether or not commercial, use of the Content in commercial publications, and the creation of value-added products using the Content. Contact: FOR FURTHER PLEASE CONTACT: BY TELEPHONE: BY E-MAIL: INFORMATION ON The Reproduction of ENDM Publication Local: (705) 670-5691 the EIP or Content Services Toll-Free: 1-888-415-9845, ext. 5691 [email protected] (inside Canada, United States) The Purchase of ENDM Publication Local: (705) 670-5691 ENDM Publications Sales Toll-Free: 1-888-415-9845, ext. 5691 [email protected] (inside Canada, United States) Crown Copyright Queen’s Printer Local: (416) 326-2678 Toll-Free: 1-800-668-9938 [email protected] (inside Canada, United States) THE GEOLOGIC SETTING OF ONTARIO The Precambrian Canadian Shield arches across Ontario separating Phanerozoic basinal accumulations of sedimentary rocks. Based on age, degree of metamorphism, and structural differences the Canadian Shield has been subdivided into geological provinces. Three of these geological provinces exist within Ontario. The oldest, largest, and most northerly is the Superior Province. South of the Superior Province exist the relatively unmetamorphosed rocks of the Southern Province and the generally highly metamorphosed rocks of the Grenville Province. Within the northern portion of the Canadian Shield lie the Hudson Bay and Moose River Basins. On the western, southern, and southeastern margins lie, respectively, the Williston, Michigan, and Appalachian Basins. Within the area of the Geological Highway Map Southern Ontario are the Precambrian rocks of the Southern Province and Grenville Province of the Canadian Shield. Overlapping onto these rocks, are the almost exclusively sedimentary Paleozoic rocks deposited within the Michigan and Appalachian Basins. Map 2418 ________________SOURCES OF INFORMATION________________ Ontario Geological Survey Geology compiled from published and unpublished maps of the Ontario Geological Survey and the Geological Survey of Canada. The following general references contain additional information about the geology and landforms of southern Ontario. Chapman, L. J. & Putnam, D. F. (1966) The Physiography of Southern Ontario; Univ. Toronto Press. A 4 map set (scale 1" to 4 mi.) accompanies this text and is available from the Ontario Ministry of Natural Resources. Chapman, L. J. (1975) The Physiography of the Georgian Bay-Ottawa Valley Area; Ontario Ministry of Natural Resources, GR 128. Hewitt, D. F. & Freeman, E. B. (1972) Rocks and Minerals of Ontario; Ontario Ministry of Natural Resources, GC 13. Douglas, R. J. W., ed. (1970) Geology and Economic Minerals of Canada; Geological Survey of Canada, Econ. Geol. Rept. 1. Cartography and design by M. J. Colman, Surveys and Mapping Branch, Ministry of Natural Resources, 1978. Highway basemap supplied by Surveys and Plans Office, Ministry of Transportation and Communications, 1977. Parts of this publication may be quoted if credit is given to the Ontario Geological Survey. It is recommended that reference to this map be made in the following form: Freeman, E. B., ed. 1978: Geological Highway Map, Southern Ontario; Ontario Geological Survey, Map 2418. PURPOSE OF MAP ' The most travelled and populated portion of Ontario lies south of highway 17 and east of Sault Ste. Marie. The purpose of the Geological Highway Map Southern Ontario is to present the general geology of this part of Ontario in relation to the familiar reference points of our highways, lakes, rivers, and communities. It is hoped that the information shown here will be of interest to the general travelling public, to students of the earth sciences, and to professional geologists. The Geological Highway Map shows by the use of colour the succession and distribution of rock units exposed at the surface. The oldest are metamor phosed volcanic rocks (unit 1) northeast of Blind River, and the youngest are the marine shales and sandstones of the Port Lambton Group (unit 38) south of Sarnia. The rock unit boundaries shown on the map have been determined or interpreted from mapping these rocks where they occur exposed in excavations or where they outcrop naturally at the surface. All of the rock units are partly covered by deposits laid down during the Quaternary glaciations, these surficial deposits consist of glacial tills and associated lake and stream deposits. They are not shown on the main map, although some are indicated on the physiographic map. All landform features, such as escarpments, canyons, hills, and valleys reflect variations in the underlying rock units and the geological processes including glaciations which have acted upon them. It is hoped that the landforms seen on your travels become more meaningful as their relationship to bedrock or geological processes is noted. G eological THE GEOLOGIC COLUMN OF TIME AND ROCK UNITS Colours and numbers are used here to represent rocks of a particular type or age. However, it should be noted that these colours usually bear no relation to the Highw ay M ap: actual colour of the rock in its outcrop. Each colour has been given a number. S o u t h e r n These numbers reflect the general sequence of rock formations with 1 being the oldest (first formed) and 38 being the youngest (last formed) rock unit shown on the map. Note that some of the rock units of the Precambrian Era may have formed simultaneously. O n t a r i o Where possible, ages in millions of years as determined by isotopic (radio metric) methods are listed in the column of time and rock units. The time relationships are best understood within the Phanerozic rock sequence and a special time column appears for these rocks. The Phanerozoic rocks are not only more recent, but contain abundant fossil life forms. From analysis of fossils and other data these rock layers have been separated into units (normally called Formations) that can be identified within widely separated outcrops. The colours on the map do not represent uniform rock compositions. Changes occur related to the rate of cooling (in igneous rocks) and to the distance from the source area (in sedimentary rocks). For example, the Lower Silurian Clinton and Cataract Groups change from dominantly sandstone-shale units in the Niagara Peninsula area to dominantly dolostone units in the Bruce Peninsula area. The distribution pattern of the coloured units (= rock units) shown on the map have been influenced by several factors: 1) the dip (tilt) of the rock layers and their thickness 2) the hardness of the rock units and their resistance to erosion 3) the topography of the land surface. Faulting (the cracking and movement of the Earth’s crust that often produces earthquakes) has affected Ontario throughout its history. Locations of the major faults within southern Ontario are shown by blue dashed lines. Faulting in Ontario has affected human history as well as geological history. For example, subsidence of the land associated with faulting created the valley lowlands of the Ottawa, Mattawa, and French Rivers.